Role of non protein amino acids in nectars: effects on bees behaviour

Floral nectar mediates interactions that are much more complex than simply alimentary relations. Nectar secondary compounds appear to have a special role in regulating interaction with other organisms. Although very few is known about their ecological roles, recently it was proved that secondary compounds may affect the nectar feeders‟ behaviour interacting with their neurobiology. We addressed a special focus on the class of non-protein amino acids. Their presence in floral nectar has been reported since long time but their ecological function has not been investigated. Data from several phylogenetically unrelated species indicate that they may represent a consistent part of the total amino acid content of floral nectar (25-45%) and generally the more abundant ones are γ-amino butyric acid (GABA) and β-alanine. The aim of the study was to test the effect of these nonprotein amino acids on bees behaviour. We tested an artificial diet consisting of sucrose solutions enriched with GABA and β-alanine at two concentrations on Bombus terrestris and Apis mellifera. Results show that B. terrestris and, only partially, A. mellifera, increase their walking activity when fed with the solution enriched with β-alanine at high concentration, while they increase their flying activity with the same solution at low concentration. Moreover, bumble bees greatly increase their survival time when fed with the solution enriched with GABA. These results push us to further consider the role of β-alanine and GABA in increasing the mobility of insects between flowers and their foraging activity and thus their pollination performances.